The Third Generation Partnership Project (3GPP) unites six telecommunications standards bodies, known as “Organizational Partners,” and provides their members with a stable environment to produce the highly successful Reports and Specifications that define 3GPP technologies. A mobile device, also called a User Equipment (UE), may operate in a wireless communication network that provides high-speed data and/or voice communications. The wireless communication networks may implement circuit-switched (CS) and/or packet-switched (PS) communication protocols to provide various services. For example, the UE may operate in accordance with one or more of an Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms “networks” and “systems” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA: includes Wideband-CDMA (W-CDMA) and Low Chip Rate (LCR) cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal Mobile Telecommunication System (UMTS). Long Term Evolution (LTE) is an upcoming release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM. UMTS and LTE are described in documents from an organization named “3rd Generation Partnership Project” (3GPP).cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). These various radio technologies and standards are known in the art.
LTE (Long Term Evolution) is a new standard for wireless communication of high-speed data for mobile phones and data terminals. It is based on the GSM/EDGE and UMTS/HSPA (Universal Mobile Telecommunication System/High Speed Packet Access) network technologies, increasing the capacity and speed using new modulation techniques. The IP-based LTE network architecture, called the Evolved Packet Core (EPC) supports seamless handovers for both voice and data to cell towers with older network technology such as GSM, UMTS and CDMA2000. The LTE technology is adapted for a smooth evolution from earlier 3GPP systems. In LTE networking, technologies such as inter-cell interference coordination (ICIC) in the frequency domain and enhanced ICIC (eICIC) in the time domain have been developed for a new heterogeneous network topology in LTE-Advanced technology.
Heterogeneous networks arose due to the rapidly increasing numbers of mobile subscribers and demand for bandwidth, and the inadequacy of traditional macro base stations to meet subscriber requirements. Homogenous networks consisting of solely traditional macro base stations may have blind spots in coverage that adversely impact user experience. With the introduction of lower power base stations, including pico cells, femtocells, and relay nodes, LTE network topology becomes a heterogeneous network (HetNet) that is able to deliver more complete coverage. In a HetNet defined in 3GPP Release 10, low power nodes (LPNs), such as RRU/RRH, pico eNB (Enhanced Node B), home eNB, and relay node, are deployed inside the macro base station or enhanced node B coverage cell.
The concept of an Almost Blank Subframe (ABS) was introduced in eICIC to address control channel interference between a macro eNB and a smaller base station such as a pico eNB in the time domain. Almost blank subframes are transmitted at low power and only contain limited signals. The interfering base station is configured to include ABSs in its transmission so that the ABS may be used by the interfered cell to provide service for the User Equipment that previously experienced strong interference. By coordinating the transmissions of the macro eNB and the pico eNB using ABS, inter-cell interference is avoided.